1. Field of the Invention
The invention is particularly concerned with the art of guiding pairs of generally vertical elements to travel linearly to one another. More particularly the invention is concerned with such a system which includes contact means generally in the form of rollers or the like supported by a first of said elements and maintaining contact with a second of said elements. Still more particularly the invention is concerned with an improved system for guiding a fork carrying carriage of a lift truck which forms a part of the mast assembly thereof upwardly and downwardly between flanged upright sections which also form a portion of said mast assembly.
2. Prior Art
In the lift truck art and in related arts wherein heavy loads are lifted generally vertically by forks, carriages, platforms, or the like which travel upwardly within a mast assembly having pairs of spaced apart uprights, rollers are generally provided which are directly rotatably attached to generally the carriage of a lift truck, for example, and which have the surfaces of said rollers contacting the inner uprights of the mast assembly. In this way, the carriage can move upwardly and downwardly without developing great frictional drag between the carriage and the mast assembly in which it rides. Often, the mast assemblies of lift trucks or the like have included one or more additional inner spaced apart upright members between the carriage and the fixed uprights and the rollers of the carriage have ridden within the inner upright members while the inner upright members themselves have had rollers extending outwardly therefrom generally at their bottoms to ride upon the interiors of the fixed uprights or upon other intermediate upright members whereby a telescoping effect has resulted allowing the carriage to ride upwardly to the total height of the inner upright members and further allowing the intermediate members themselves to travel upwardly to their respective heights within the fixed uprights.
A problem which has constantly existed in the art has been that the rollers, whether they be the rollers rotatably attached to and extending from the carriage or the rollers rotatably attached to and extending from the inner or intermediate upright members, have borne strongly against the respective one of the intermediate members or the fixed uprights thereby creating highly stressed contact areas with resulting flaking of the member being borne upon by the rollers. The present invention is concerned with a unique system for guiding generally vertical elements to travel linearly relative to one another whereby the amount of stress at each point of contact between rollers and vertical elements has been greatly reduced. It will be apparent that such guidance system is particularly useful when a telescoping system is utilized since in this instance when heavy loads are lifted well off the ground the stress which develops adjacent ground level is multiplied by the effective lever arm created by the additional extension provided by the telescoping means. Thus, the guiding system of the present invention is particularly useful in such applications as lift truck mast assemblies in which heavy loads are picked up and wherein these heavy loads are generally picked up from a position removed from the mast assemblies which situation tends to pull the rollers into hard contact with the elements in which they slide because the loads sit upon forks, platforms or the like extending from the carriage.